Interpretive Summary: A principal goal of current research on insect pest control in apples and pears is to develop methods of controlling pests that will allow growers to make fewer applications of insecticides potentially harmful to the environment and human health. At the USDA-ARS Yakima Agricultural Research Laboratory in Wapato, WA, one approach being investigated is to evaluate the potential of native habitat near orchards to act as sources of natural enemies (predatory and parasitic insects and spiders) that can move into the orchards and contribute to control of pest insects. In south-central Washington the most common native habitat near orchards is sagebrush steppe, an association of shrubs and herbaceous plants adapted to the area’s desert-like climate. For this study, we collected and identified nearly 29,000 spiders and predatory and parasitic insects from seven common species of native plants that occur in sagebrush steppe habitat. We found that 49% to 99% of the predatory insects and spiders collected on the plants belonged to species also found in nearby orchards where they feed on pest insects. None of the nearly 6,000 parasitic insects, however, belonged to species known to parasitize orchard pests. Because sagebrush steppe is a likely source of some of the predators found in orchards modest efforts at its conservation or enhancement in the vicinity of orchards may benefit biological control of orchard pests.

Technical Abstract:
Four native shrubs and three native, perennial, herbaceous plants common in sagebrush steppe habitats of eastern Washington were sampled for beneficial arthropods with a beat tray. Sagebrush steppe is the most frequently encountered natural habitat adjacent to apple and pear orchards in this part of the state. Many predatory arthropod species found on the plants also occur in local orchards and some of these species were particularly abundant when plants were in flower. Other predatory arthropod species found on the native plants rarely occur in local orchards. Of the natural enemies also found in orchards the most abundant was Orius tristicolor (White, 1879) whose numbers were very high on some plant species while they were in flower. Other predatory Hemiptera also found in local orchards included Deraeocoris brevis (Uhler, 1904), Nabis alternatus Parshley, 1922, and Geocoris spp. Members of the Coccinellidae, Chrysopidae, and Hemerobiidae were not common on the sagebrush plants, but one or more species in each family that commonly occur in orchards were collected. Spiders collected on the native plants that also occur in orchards included Misumenops lepidus (Thorell, 1877), Xysticus cunctator Thorell, 1877, Sassacus papenhoei Peckham & Peckham, 1895, Phidippus spp., Oxyopes scalaris Hentz, 1845, and Meioneta fillmorana(Chamberlin, 1919). Parasitoids, almost all of which were Hymenoptera, were collected on all plants, but species of known importance in orchard biocontrol were not found.